Update:The Wall Street Journal was told that characters from the Marvel and Star Wars universes are being developed for future versions of Infinity.

Arriving on multiple consoles and pc last August, Disney's Infinity features characters and elements from such franchises as Cars, The Incredibles, Monsters Inc., and Pirates of the Caribbean. Could recently acquired properties, such as the Marvel Universe and Star Wars, be added at some point? Disney Interactive VP of product development Bill Roper says they are looking at every license available to them. "...I never discount any possibilities with the vast array of characters and worlds that we can tap into across the company...We love the potential for Infinity. We always joke, well, 'the possibilities are infinite."
(Source: IGN.com)